Update code-generator to 1.30.1

[xrstf]

While working on #293, I noticed I had to bump the code-generator as well, which blew up that PR more than it should. So this PR extracts just the code-generator update.

The code generator was significantly outdated and was updated to match the current set of Kube dependencies (i.e. 1.30.x). Notably:

• The entire GOPATH cloning logic was removed; all generators are now compatible with Go modules and there is no need anymore to ensure a GOPATH-like setup (I ran everything locally in ~/projects/prow).
• The GOPATH magic mentions bazel peculiarities as one of the reasons for the complexity. I could not immediate see where exactly Bazel is currently used in Prow, so I simply chose to ignore it and see which wall I would hit. 😁 Bazel support seems to have been removed 2 years ago via Bazel build/test instructions are replaced with make rules kubernetes/test-infra#26039.
• Not working in a mirrored version also fixed the bindata generation: That step never actually copied the files back to the repository and so we never noticed that someone manually fixed the %v to be %w, because go-bindata 3.1.3 (latest) still outputs %v.

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[netlify]

✅ Deploy Preview for k8s-prow ready!

Name	Link
🔨 Latest commit	3c46998
🔍 Latest deploy log	https://app.netlify.com/sites/k8s-prow/deploys/670ba7c1d10710000872e894
😎 Deploy Preview	https://deploy-preview-298--k8s-prow.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[xrstf]

/test all

[petr-muller]

/cc

[xrstf]

@petr-muller This is currently blocking my other PRs :-)

[petr-muller]

LGTM

Thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: petr-muller, xrstf

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [petr-muller]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment